Achieved results and methods
During the 2nd phase of MARIE, a 240 GHz MIMO radar system was designed (Fig. 1). It consists of eight transceiver MMICs, placed horizontally and vertically (Fig. 1c), Fig. 2a)) and a 120 GHz signal source MMIC (Fig. 2b)). The signal source MMIC, housing a Voltage Controlled Oscillator (VCO), is placed at the corner, providing a differential output signal leading to both horizontally and vertically aligned transceivers. The Local Oscillator (LO) signal is distributed via two ribbon bond wires and is daisy-chained along the transceivers. In Fig. 2c), the measurement data of one receive channel using one transmitter is displayed. For the measurement, a reflector was placed at a distance of 22 cm.
Additionally, the 2nd phase involved investigating various vector modulators [1, 2]. The core structure of these modulators is identical, featuring a branchline coupler to provide I-Q signal generation and two controllable amplifiers for each of the I-Q signals. With two amplifiers, the polarity of the I or Q path can be switched to provide an output phase in the entire angular range (Fig. 3). The 4-bit digital vector modulator provides eight different phase states, similar to an 8-PSK modulation.
Moreover, the same digitally controlled vector modulator coupled with a tunable branchline coupler was designed (Fig. 4) [3]. The design offers the advantage of covering a significant portion of the entire 360° range using only one analog control voltage. The constellation diagram for this system is presented in Fig. 5, showcasing how the digital states of the vector modulator shift with the tunable branchline coupler. In the context of investigating a phased-array system with multiple transmit chains with an amplifier, this approach significantly reduces the number of required digital to analog converters.
Furthermore, in close collaboration with C02 and C05, a 480 GHz FMCW transceiver MMIC was developed in IHP’s SG13G3 SiGe technology [4]. This transceiver integrates signal generation using a 120 GHz VCO and a frequency divider for external PLL utilization and chirp generation. The subharmonic receiver mixer operates with 240 GHz quadrature signals. By employing a push-push frequency doubler and a single-ended patch antenna, the transmit signal reaches a power of -9.4 dBm (Fig. 6 left). The photograph of this transceiver is depicted in Fig. 6 right.
Also, C02 and C03 developed a 360 GHz differential signal source (Fig. 7 left), which offers a continuous tuning range of over 106 GHz (Fig. 7 right) [5]. It incorporates a VCO with a divide-by-16 prescaler, multiple frequency doublers, and power amplifiers.
Finally, C03 and C05 investigated the impact of group delay dispersion on radar imaging quality utilizing multi-resonant on-chip antennas [6]. A system model based on a 240 GHz FMCW radar system with one transmit and 16 receive antennas was created for analysis. The antennas are equidistantly placed with a distance of 0.5 λc. For the simulation, measurement data of a multi-resonant circular polarized on-chip antenna, also used in the 240 GHz transceiver MMIC, were used. Fig. 8(a) and Fig. 8(b) show the imaging results with the impact of group delay dispersion in cross section and cross range, respectively.
Selected project-related publications
[1] J. Wittemeier, M. A. Yildirim and N. Pohl, "Compact and Digitally Controlled D-Band Vector Modulator for Next-Gen Radar Applications in 130 nm SiGe BiCMOS," IEEE Journal of Microwaves, April 2023, [DOI: 10.1109/JMW.2023.3250340]
[2] J. Bott and N. Pohl, “A Multipurpose D-Band Vector Modulator for FMCW and PMCW Sensing Applications in 130 nm SiGe”, IEEE Transactions of Microwave Theory and Techniques, February 2024, [DOI: 10.1109/TMTT.2024.3365945]
[3] J. Bott, F. Vogelsang, and N. Pohl, ”A D-Band Phased-Array Chain Based on a Tunable Branchline Coupler and a Digitally Controlled Vector Modulator," IEEE Journal of Microwaves, January 2024, [DOI: 10.1109/JMW.2023.3318528]
[4] D. Starke, J. Bott, F. Vogelsang, B. Sievert, J. Barowski, C. Schulz, H. Rücker, A. Rennings, D. Erni, I. Rolfes, N. Pohl, "A compact and fully integrated 0.48 THz FMCW radar transceiver combined with a dielectric lens," International Journal of Microwave and Wireless Technologies, December 2023, [DOI: 10.1017/S1759078723001368]
[5] D. Starke, F. Vogelsang, J. Bott, J. Schöpfel, C. Bredendiek, K. Aufinger and N. Pohl, “A 360 GHz Fully Integrated Differential Signal Source With 106.7 GHz Continuous Tuning Range in 90 nm SiGe:C BiCMOS,“ IEEE Transactions on Microwave Theory and Techniques, February 2024, [DOI: 10.1109/TMTT.2024.3356610]
[6] B. Sievert, J. Wittemeier, J. T. Svejda, N. Pohl, D. Erni and A. Rennings, "Bandwidth-Enhanced Circularly Polarized mm-Wave Antenna With On-Chip Ground Plane," IEEE Transactions on Antennas and Propagation, October 2022, [DOI: 10.1109/TAP.2022.3184539]
[7] J. Wittemeier, B. Sievert, M. Dedic, D. Erni, A. Rennings and N. Pohl, "The Impact of Group Delay Dispersion on Radar Imaging With Multiresonant Antennas," IEEE Microwave and Wireless Components Letters, March 2022, [DOI: 10.1109/LMWC.2021.3128281]
[8] B. Sievert, J. Wittemeier, J. T. Svejda, N. Pohl, D. Erni and A. Rennings, "Coaxial Cable Based Magnetic and Electric Near-Field Probes to Measure On-Chip Components up to 330 GHz," IEEE Antennas and Wireless Propagation Letters, October 2023, [DOI: 10.1109/LAWP.2023.3291571]
[9] B. Sievert, J. T. Svejda, J. Wittemeier, N. Pohl, D. Erni and A. Rennings, "Equivalent Circuit Model Separating Dissipative and Radiative Losses for the Systematic Design of Efficient Microstrip-Based On-Chip Antennas," IEEE Transactions on Microwave Theory and Techniques, February 2021, [DOI: 10.1109/TMTT.2020.3040453]
[10] J. Bott, D. Starke, F. Vogelsang, J. Schöpfel, C. Bredendiek, K. Aufinger, and N. Pohl, "A 335–407-GHz SiGe-Based Subharmonic Mixer Using a Fully Integrated LO Generation," IEEE Microwave and Wireless Technology Letters, April 2024, [DOI: 10.1109/LMWT.2024.3389061]
